How many characters does the longest word from this page contain?Consider 'institutionalists', which has 17 letters.
What's the highest scoring word you can play in Scrabble ?You can make 'inquests' which scores 17 points.
Which word on this page is the most common?A popular word for the combination you requested is 'interests'.
How many words are possible to put together using the specified combination?From this page of words starting with 'i' that contain 'sts', you have 36 entries which are possible altogether.